Preservative Challenge Testing (PET)
What is Preservative Challenge Testing (PET)?
A report on control of deliberately introduced microorganisms.
Why do you need this service?
Request it for a new formula or when a change may affect preservation, such as altered pH, preservative concentration or raw materials. The need for testing and retesting should follow a documented risk assessment, not an assumed universal annual schedule.
Who provides Preservative Challenge Testing (PET) services?
Companies linked to Preservative Challenge Testing (PET) or a more specific service
Certified Cosmetics
Certified Cosmetics provides cosmetic safety assessments, product files, notifications, label reviews and laboratory-testing coordination from Almere.Preservative challenge testing
The laboratory selects a method appropriate to the product, intended use and specification. ISO 11930 addresses antimicrobial protection of cosmetics. USP chapter 51 or Ph. Eur. 5.1.3 may apply in other product or specification contexts, but these methods are not automatically interchangeable.
Protocol and recovery controls
The agreed method defines the challenge organisms, inoculation procedure, storage conditions, sampling points and acceptance criteria. Counts are assessed by organism and time point rather than against invented limits for broad product categories.
Neutralization and microbial recovery must be suitable for the formula. If residual preservative continues to inhibit organisms during counting, an apparently favorable result may reflect analytical interference rather than the product’s actual performance.
Reporting the result
The report should identify the tested sample, method, controls, counts and interpretation against the selected criteria. Deviations and method limitations should be explicit. A result applies to the formula and conditions tested, not automatically to later reformulations, different packaging or all foreseeable consumer handling.
Challenge testing contributes to the preservation assessment. It does not replace manufacturing hygiene, routine microbiological quality control or evaluation of protection as the product ages.
Deliverables and limitations
Request a report identifying the sample and method version, suitability checks, initial and subsequent microbial counts, calculated log reductions, deviations and the applicable conclusion. Any qualified result or additional protective factors used in interpretation should be explained. Agree sample requirements and laboratory scheduling directly rather than assuming a standard turnaround.
A satisfactory challenge result supports the preservation evidence for the tested sample and conditions. It does not establish shelf life, rule out manufacturing contamination or guarantee protection during every consumer use scenario. Combine it with formula, packaging and use-context review when a broader preservation decision is required. Antimicrobial activity of a cosmetic active is a separate testing question.
Assess cosmetic microbiological quality through challenge testing, contamination screening and preservation studies, with each test question defined. Explore another Microbiological Testing page on cosmetic-labs.com.